Pier-supported refractory constriction element

ABSTRACT

A refractory constriction element for large-diameter fluid bed reactors is supported by vertical refractory piers located within the windbox.

This invention is directed to a novel refractory constriction elementfor a fluidized bed reactor having a hot windbox.

Fluidized bed reactors, which are very suitable for carrying outoperations at elevated temperatures such as roasting, calcining andincineration, may very broadly be classified as either cold-windbox orhot-window reactors. In this classification, the cold windbox meansmerely that air or another gas at substantially ambient temperature isintroduced into the windbox as the fluidizing gas, whereas the gasesdelivered to the hot windbox are at an elevated temperature, say500°-1800° F. Constriction plates for cold windbox reactors are commonlyconstructed of steel, and if the diameter of the constriction plate islarge, additional steel beams or support members may be provided in thecold windbox. A constriction plate of this type may be as large asrequired for the particular application and no limit is imposed on thissize by the structural material used. A very different problem exists inthe reactors designed to operate with hot windboxes, where theconstriction dome is made from a refractory ceramic material. In suchreactors a "sprung arch" type of construction is used in which theconstriction element, which is flat on top, nevertheless presents anarched or dome-like configuration due to the concave bottom surface ofthe element. This is a true dome and it has reached its designlimitations at about the 20 to 22-foot diameter with which certainreactors in service have been provided.

While the term "refractory" is sometimes used to describe metals whichretain useful properties at elevated temperatures, in this descriptionthe term is employed only to describe materials of the ceramic type,such as pre-fired fire clay.

It is recognized that a need exists for a refractory constrictionelement construction which will satisfy the requirements of fluid bedreactors having diameters substantially greater than 20 feet (6.1meters).

It is an object of this invention to provide an improved supportstructure for large-diameter refractory constriction elements.

It is a further object of this invention to provide an improvedconfiguration for a refractory constriction element.

Other objects and advantages of the present invention will becomeapparent from the following description taken in conjunction with theaccompanying drawings in which:

FIG. 1 is an elevational view, partially in section, of a fluidized bedreactor incorporating pier supports for a refractory constrictionelement in accordance with the present invention,

FIG. 2 is an enlarged elevational view in section of a pier constructedin accordance with this invention,

FIG. 3 is a plan view of a refractory module for the constrictionelement of this invention,

FIG. 4 is a view in elevation of the refractory module of FIG. 3,

FIG. 5 is a plan view of one quadrant of the constriction element ofthis invention showing the placement of fuel guns and tuyeres,

FIG. 6 is an enlarged view in section of a tuyere and tuyere port, and

FIG. 7 is an elevational view in section of a modified form of theconstriction element of this invention.

Generally speaking, the refractory constriction element of the presentinvention is supported by refractory piers which extend through thewindbox and are themselves supported by the bottom wall of the windbox.

The constriction element is comprised of a plurality of refractoryelements or modules which are maintained in their predeterminedhorizontal positions, though subjected to expansive and contractiveforces upon heating and cooling, by contact with each other and with thewall of the reactor vessel. The piers are fixed in their positionrelative to the constriction element since they fit into recessesprovided in the bottom surface of the constriction element. The piersare hollow, with a passageway provided centrally thereof. Fuel guns areintroduced through passageways in the bottom wall of the windbox, thenthrough the central passageways of the piers and finally throughsuitable passageways provided in the constriction element, thus gainingaccess into the reaction chamber. A metal sealing sleeve is providedthroughout the length of the passageways in these refractory members.This sleeve lines the passageways, thus aiding in maintaining theposition of the several elements, and also provides a sealing flangewhich rests on the top of the constriction element around the opening ofthe passageway in the reaction chamber.

The constriction element is composed of refractory modules which may beintegral castings, or made up of a plurality of mutually-supportedrefractory members or shapes. The modules are supported on the piers atthe four corners thereof, with each pier providing partial support forfour modules.

The diameter of the reactor in which the constriction element of thepresent invention is located, makes it impractical to rely entirely onfeeding fuel into the fluidized bed through the side walls of thereactor. The fuel introduced through such side fuel guns penetrates onlya limited distance into the reactor before combustion occurs andtherefore it is desirable to introduce fuel into the central region ofthe constriction element through vertical fuel guns. The fuel guns areinstalled axially of the refractory piers to protect the fuel guns fromthe hot gases in the windbox.

The pier support provided in accordance with this invention makespossible a constriction element configuration not conceivable in astructure lacking the pier support. Thus, it is possible andadvantageous to provide the constriction element with a dished ordepressed center. Such a "reverse" constriction dome provides a deeperbed in the center of the reaction chamber and there is consequently lesstendency for a disproportionately large amount of air to channel throughthe center of the bed as sometimes happens with the presently employedflat-topped sprung domes. In addition, such a reverse dome resists thetendency of the constriction element to be lifted by excess air flow.

Referring now to the drawings, in FIG. 1 there is shown a fluidized bedreactor 10 which incorporates the vertical refractory pier supports 45and a disk-shaped constriction element 21 in accordance with the presentinvention. Thus, the fluidized bed reactor 10 has a vessel wall 11 whichcomprises a steel shell 13 and a refractory ceramic lining 14. Thereaction chamber in the upper portion of the fluid bed reactor 10 isseparated from the windbox 17 in the lower portion of the fluid bedreactor by the constriction element 21. A feed conduit 19 is providedfor introducing feed stock into the reaction chamber 15. Theconstriction element 21 is provided with a number of tuyeres 22 forproviding communication between the hot windbox 17 and the reactionchamber 15. A fluidized bed 24 is illustrated in the reaction chamber 15and a conduit 26 is provided for removal of solid particulate products.A hot gas conduit 29 is provided for supplying fluidizing gas or air tothe hot windbox 17. Conduit 31 is provided for the off-gases emanatingfrom the reaction chamber 15. Side fuel guns 32 are provided forinjecting fuel through the side wall 11 of the reactor, while bottomfuel guns 34 are vertically oriented and penetrate the windbox bottomwall 36, the windbox proper and the constriction element 21. Areinforcing band 27 surrounds the steel shell 13 at the level of theconstriction element 21 to resist any shifting of the members thatcomprise the constriction element 21. It will be noted that the fluidbed reactor 10 is supported by the beams 41 under and in contact withthe windbox bottom wall 36 and that legs 43 support the entire reactorstructure in its elevated position.

In FIG. 2 further details of a load-bearing pier 45 and relatedstructure are shown in some detail. The pier which is composed of aplurality of refractory shapes which may be circular or square incross-section, extends between the windbox bottom wall 36 and therefractory constriction element 21 to support the latter. The refractoryshapes 51, 52 and 54 are mortared at the joints thereof to form theunitary pier structure 45. The refractory shapes are prefired membersand are hollow along the longitudinal axes thereof so that alignment ofthe refractory shapes provides an elongated passageway 56 through thestructure. While the pier 45 has been shown as a refractory membercomposed of a plurality of elements, it should be understood that thepier might be cast as a single member, prefired and used in that form.

The pier 45 illustrated in FIG. 2 is arranged to accommodate a verticalfuel gun and for that reason is aligned with the vertical holes orpassageways 49 in the windbox bottom wall 36 and the hole or passageway53 provided at the corners off the modules 61 (as will be describedhereinafter) which form the constriction element 21. A sealing sleeve 57is provided which runs through the aligned passageways 49, 56 and 53,respectively, in the windbox bottom wall 36, the refractory shapes ofpier 45 and the refractory element 21. This sleeve will be composed ofmetal such as alloy steel and is provided at the upper end thereof witha sealing flange 58 which rests on the top surface of the constrictionelement 21 and has the function of preventing leakage of fuel from thereactor chamber 15 to windbox 17 along the passageway 53. The topmostrefractory shape 54 projects into a recess 59 provided in theconstriction element 21 to positively locate the pier structure. Aportion of the reactor shell 13 with its refractory lining 14 andsupport beams 41 is also visible in FIG. 2. In FIGS. 3 and 4 a roughlysquare module 61 of the type employed to form the constriction element21 is illustrated in plan and elevational views. It will be seen thatthe module 61 is composed of a plurality (in this case, sixteen) ofbrick-like refractory shapes. The corner refractory shapes 62 havequadrant cutaways which with adjoining modules will form a circularpassageway 53 such as that illustrated in FIG. 2. In addition, thecorner refractory shape 62 has at the bottom thereof a quadrant recesswhich together with adjoining modules forms the recess 59 which receivesthe topmost refractory shape 54 (again as illustrated in FIG. 2) of pier45. The refractory shapes 62 are provided with a supportive inclinedsurface 64 which with a complementary surface on the supportedrefractory shapes 63 makes each module self-supporting, provided themodules are restrained against horizontal movement. The joints betweenthe refractory shapes may, of course, be joined with refractory mortar.Each of the refractory shapes is provided with a tuyere port 66.

It should be noted that the module 61, rather than being formed of aplurality of individual refractory shapes, may be formed as a unitarymember from a castable refractory material.

FIG. 5 shows the relationship of the fuel guns (both side fuel guns andbottom fuel guns) and the constriction element modules. A quadrant ofthe constriction element is illustrated in the figure and it will benoted that a plurality of side fuel guns 32 are also illustrated. Themodules 61 forming the constriction element 21 are all provided withtuyeres 22. In the central region of the constriction element, where thefuel from fuel guns 32 cannot be expected to penetrate, the constrictionelement 21 is provided with the vertical fuel guns 34. As will be noted,and this has been explained hereinabove, the fuel guns are located atthe corners of the modules 61.

FIG. 6 illustrates a typical non-sifting tuyere 22 positioned in thetuyere port 66 in the constriction element 21. The tuyere 22 has acentral bore 23 which acts as a plenum chamber for the horizontal ports28 provided in the tuyere.

FIG. 7 illustrates a modified form of the refractory element illustratedin FIG. 1. The modified refractory constriction element 48 has adepressed central portion thereof 47 which constitutes in effect a"reverse dome." This structure has two principal advantages, one beingthat the inverted dome structure resists lifting forces developed by theair pressure in the windbox, and, since the center of the fluidized bedon the constriction dome 48 is deeper in the center than at the edges,air introduced through tuyeres 22 into the central region of the bed isless likely to channel through the bed at the center thereof, and a moreuniform distribution of air can therefore be achieved. This modifiedform of the invention also shows the provision of a blanket ofinsulation 42 surrounding the reactor shell 13 below the level of theconstriction dome 48. The purpose of the insulating blanket 42 is tominimize the differential dimensional change between the constrictiondome 48 and that portion of the steel shell 13 which forms a part of thewindbox bottom wall 36. Thus, in a structure lacking the insulatingblanket 42, upon heating, the constriction dome 48 would tend to expandmore than the windbox bottom wall 36 exposed as it is to ambienttemperatures. The windbox bottom wall 36 would therefore expand lessthan the constriction dome 48 and the top of the piers 45 would tend tomove radially outward more than the base of the piers. Such tilted piersthreaten the support and therefore the integrity of the constrictiondome 48. It is preferable, too, that the insulating blanket 42 surroundand insulate the support beams 41 as well as the reactor shell 13 sincethe support beams are in contact with the reactor shell. The insulatingblanket may, of course, also be provided on the embodiment shown in FIG.1.

There has thus been disclosed a novel refractory constriction elementstructure which is particularly suitable for fluidized bed reactorshaving large bed diameters and in which a hot windbox type of operationis employed. While the illustrated embodiments of the invention allincorporate fuel guns, in some circumstances fuel guns are not requiredin the reactor, and in such cases, the piers may be solid refractoryshapes rather than the pierced shapes shown. Also, in those parts of thereactor where vertical fuel guns are not employed, the longitudinalpassageways in the piers and constriction element may be plugged withrefractory mortar.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention, as those skilled in the art will readilyunderstand. Such modifications and variations are considered to bewithin the purview and scope of the invention and appended claims.

I claim:
 1. A fluid bed reactor comprising a reaction chamber, a hotwindbox having a bottom wall, said hot windbox being partitioned fromsaid reaction chamber by a refractory constriction element, saidconstriction element having a diameter greater than twenty feet (6.1meters) and adapted to support thereon a body of particulate solidssubject to fluidization, a plurality of elongated load-bearingrefractory piers extending between said bottom wall and saidconstriction element to support said element, said piers extending intocontact with positioning means provided on said constriction element,said piers each having a longitudinal passageway therethrough foralignment with vertical mating passageways in said bottom wall and saidconstriction element, and vertical fuel guns positioned in at least someof said aligned passageways for introducing fuel into said reactionchamber.
 2. The fluid bed reactor of claim 1 wherein the structure ofthe constriction element is such that the weight thereof is exerted uponsupporting structure substantially without a horizontal component andwherein each of said fuel guns extends from below said windbox throughthe aligned passageways in said bottom wall, said pier and saidconstriction element and projects into said reaction chamber above saidconstriction element.
 3. The fluid bed reactor of claim 2 wherein theconstriction element has a disk-like configuration and wherein saidlongitudinal passageway in said piers and said vertical matingpassageways in said bottom wall and said constriction element areprovided with a sealing sleeve lining the passageways and having asealing flange at the upper end thereof which is in contact with the topsurface of said constriction element about said fuel gun.
 4. The fluidbed reactor of claim 3 wherein said constriction element comprises aplurality of roughly square refractory modules each supported at thefour corners thereof by four of said refractory piers, said modules eachhaving a plurality of tuyere ports therein.
 5. The fluid bed reactor ofclaim 4 wherein said refractory modules each comprise a plurality ofmutually supportive refractory shapes spanning the distance betweenadjacent piers.
 6. The fluid bed reactor of claim 5 wherein saidconstriction element has an inverted dome configuration.
 7. The fluidbed reactor of claim 6 wherein said positioning means comprise recessesin the windbox side of said constriction element in which the upperextremities of said piers are seated.
 8. The fluid bed reactor of claim3 wherein the constriction element has a configuration presenting adepressed concave surface to the reaction chamber.
 9. The fluid bedreactor of claim 3 wherein said fluid bed reactor comprises a vesselcomposed of a steel shell with a refractory lining and wherein thatportion of said steel shell which contains said windbox is entirelyenveloped within an insulating layer so that the differential thermalexpansion and contraction of said constriction element and said bottomwall is minimized, thereby limiting differential lateral movement ofsaid load-bearing piers.
 10. The fluid bed reactor of claim 4 whereinsaid constriction dome has an inverted dome configuration.
 11. A fluidbed reactor comprising a reaction chamber, a hot windbox having a bottomwall, said hot windbox being partitioned from said reaction chamber by arefractory constriction element, said constriction element having adiameter greater than twenty feet (6.1 meters) and adapted to supportthereon a body of particulate solids subject to fluidization, aplurality of enlongated load-bearing refractory piers extending betweensaid bottom wall and said constriction element to support said element,said constriction element comprising a plurality of roughly squarerefractory modules, each supported at the four corners thereof on fourof said refractory piers, each of said modules comprising a plurality ofmutually supportive refractory shapes spanning the distance between thepiers supporting each module, said modules each having a plurality oftuyere ports therein and the upper extremities of said piers extendinginto recesses formed in the windbox side of said refractory modules toposition said piers.